Fix ZLIB_LIBRARIES var on macOS

extern/zlib/CMakeLists.txt

@@ -1,7 +1,7 @@
 if (APPLE)
 # use toolchain zlib
 find_package(ZLIB REQUIRED)
-set(ZLIB_LIBRARIES ZLIB::ZLIB)
+set(ZLIB_LIBRARIES ZLIB::ZLIB CACHE STRING "zlib libraries" FORCE)
 else()
 if(NOT WIN32 AND NOT NX) # remove WIN32 when specter/freetype is gone
 find_library(ZLIB_LIB NAMES zlib z)
@@ -37,11 +37,11 @@ install(TARGETS z DESTINATION lib COMPONENT zlib)
 else()
 target_compile_options(z PRIVATE -Wno-implicit-fallthrough)
 endif()
-set(ZLIB_LIBRARIES z CACHE PATH "Zlib libraries" FORCE)
-set(ZLIB_INCLUDE_DIR ${CMAKE_CURRENT_SOURCE_DIR} CACHE PATH "Zlib include path" FORCE)
+set(ZLIB_LIBRARIES z CACHE STRING "zlib libraries" FORCE)
+set(ZLIB_INCLUDE_DIR ${CMAKE_CURRENT_SOURCE_DIR} CACHE PATH "zlib include directory" FORCE)
 else()
-set(ZLIB_LIBRARIES ${ZLIB_LIB} CACHE PATH "Zlib libraries" FORCE)
+set(ZLIB_LIBRARIES ${ZLIB_LIB} CACHE PATH "zlib libraries" FORCE)
 find_path(ZLIB_INCLUDE_DIR zlib.h PATHS "${PNG_LIB}/../../include")
 message(STATUS "Using zlib at ${ZLIB_LIB}, include: ${ZLIB_INCLUDE_DIR}")
 endif()
-endif()
+endif()